الفهرس 
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Abstract
The strategy of this work is based on the utility of the two international codes, GAUSSIAN 98 and CRYSTAL 98 to perform simulations of ionic crystals to clarify how the ab initio level of the quantum theory deals with the insulators.
The former code, GAUSSIAN 98, was used to simulate LiH and AgBr crystals. The study of LiH aimed to compare the stabilities of the perfect- and defect-containing, (H-center), surfaces of the LiH crystals at different orientations; (110) and (111) in terms of the adsorption phenomena and calculating some related properties. The study of AgBr crystal aimed to examine the (001) surface-laser activity (FA-center: Sc2+ and La2+) based on Stockes shifted optical transition bands. Valence and conduction bands of the ground-states, the HOMO and LUMO of the low-lying excited-states, energy barriers to orientational destruction of FA, defect formation energies, and exciton bands were also examined.
The later code, CRYSTAL 98, was employed to simulate the alkaline-earth oxide-crystals; MgO, CaO and SrO at three different surfaces, namely; (001), (110) and (210). The simulation in this case was devoted to study some structural properties concerning the surface morphology of these crystals in terms of their binding energies, surface formation energies and relaxation energies. The adsorption phenomena at the surfaces of these oxides were also studied using atomic and molecular species namely; atomic oxygen and molecular water. Another goal of this part is to perform calculations on the stability of the peroxide ion as well as related properties such as charge density, electrostatic potentials and vibrational analysis.